It is well known that during the injection moulding of articles of thermoplastic material, it is necessary to provide a duct for feeding the molten material, which at the end of the injection operation remains partly attached to the article. This requires a subsequent finishing operation which obviously increases the cost of the product.
As the known system for dispensing with the finishing operation subsequent to the moulding are of necessity based on types of capillary injection (commonly known as submarine or tunnel injection), they lead to internal stresses in that zone of the article which is close to the point of injection. These stresses are extremely damaging to the physical-mechanical characteristics of the article.